Touch sensitive input for Sonic Pi


Development of a touch sensitive keyboard for use with Sonic Pi, using Adafruit’s MPR121 12 toiuch sensitive input board with OSC support added to the software.

Full article, with link to software is here.

Video of project in action is here.


Sonic Pi 3 Player /Recorder version 1.2

Now released version 1.2 of my Player ?recorder for Sonic Pi 3 utilising a TouchOSC interface. This has expanded considerably since version 1, but as a result is now is not suitable for use on a Pi3. Also, as the program has increased in length it now needs to be run using the run_file command from a text file.(.rb)

Full details of the interface and usage are contained in a page here including a link to the code.

LightshowPi drives a sensehat using Sonic Pi

Two years ago I produced a video showing the then Sonic Pi 2.7 driving the leds on a sense-hat using hacked lightshowPi software using the then current version. I didn’t write up the software which was quite complex, but merely posted a video of the system operating on youtube. Recently I was asked on twitter if I could share the code, as some students in California wanted to try it out. I managed to located the SD card containing the software, and fired it up on a Raspberry Pi2 using the then prevalent Sonic Pi and operating system and got it working. I then decided to see if I could update it to run on the latest OS on a Pi3 and with a later version of Sonic PI. I have now managed to do this and am publishing the code so that others can try it out.

The system also requires an external USB audio card, to give an audio input that can be used by LightshowPi. I used a sabrent usb module which I obtained on Amazon (UK) which is also available in the states here Three other pieces of hardware are required (apart from a sensehat!). A two way stereo audio splitter lead (3.5mm jack to 2 3.5mm sockets), a stereo 3.5mm jack to jack lead, and a short usb extender lead as the Sabrent audio card is a little fat to plug into the Pi directly.

System overview
PLug the sensehat into a Pi3 running Raspbian Stretch, set the default audio to the built in bcm2835 ALSA card using Prefereces=> Audio Device Settings on the Pi main menu. Click Select Controls if you can’t see the Playback slider, and make sure it is active and at maximum, before clicking OK and start Sonic Pi running. Use a “punchy” piece like my sparkling tom-toms for best effect. The audio output from this is fed to a two way splitter plugged into the audio out 3.5mm socket on the Pi. One of these outputs goes to an external audio amp so you can hear the sound, the other is fed to the microphone input on the Sabrent USB audio card. This supplies an audio feed to the modified lightshowpi code. You can see the wiring below. The dual splitter plugged into the 3.5mm audio out socket, with a red lead going to an audio amplifier and speakers (out of the photo) and the white lead fed back into the microphone input to the Sabrent usb audio card which is plugged into the Pi via a short extender lead, as it is rather fat to plug in directly. Other leads are to the hdmi monitor, the power supply and to a usb keyboard and usb mouse (all out of the picture).

Install the current version of lightshowpi using the instructions at

Download my modified code for lightshowpi from here  and copy the file to the top level of the lightshowpi folder. Right-click the file lsp_sensehat.tar.gz (in the gui) and select extract here, and two folders will be created, py_sensehat and sensehat_config These contain the modified files set up to utilise the sense hat rather than individual leds connected to the gpio pins. Essentially this is based on an earlier version of lightshowpi. The reason for installing the latest version is to install the various background files and utilities used by the lightshowpi files. You can see the contents of the lightshowpi folder with the two additional folders from the lsp_sensehat.tar.gz file below.
Before starting to use the system, you should check that the microphone input sensitivity is setup. to do this select Audio Device Settings from Preferences on the Raspberry Pi main menu. Select the USB Audio Device (Alsa mixer) from the Sound Card list at the top, click Select Controls and select Speaker and Microphone from the list (NOT Microphone Capture). Click Close, and adjust the Microphone slider to maximum, and make sure it is enabled in the box below the slider. You can disable the Speaker output in the left hand box below the two Speaker sliders as we are not using audio output via the USB card. Then close the Audio Device Settings window. NB make sure that bcm2835 ALSA is still marked as default, as shown in the FIRST Audio Device Settings picture above. Below you can see the settings for the USB Audio card.
To start lsp running do the following from a terminal:

cd ~
cd lightshowpi/py_sensehat
sudo python

You should see the message Running in audio-in mode, use Ctrl+C to stop on the screen. All being well, if you start Sonic Pi playing then after a pause of a few seonds as audio samples are built up by lightshowpi the sensehat leds should start flashing in response to the music You need quite loud music for it to work.

How does it all work?
I’m not going to go into great detail, as it would take too long, but I can give one or two pointers. Lightshowpi is a system which can take an audio input from an audio input or from a music file eg .wav, .mp3 and analyse it using fast fourier transforms to produce a series of outputs for different ranges in the audio spectrum. These can then be channeled to control LEDs connected to the gpio pins on the raspberry pi. What I have done is to hack the code that channels the outputs to the gpio pins, and instead send them to a python program within the py_sensehat folder which contains a series of function which can control LEDs on the sense hat. In the program I use columns of LEDs coloured with a rainbow, which can be switched on or off. using turn_on_light(num) and turn_off_light(num). These two commands are used in the hacked program in the py_sensehat folder, replacing calls to wiringpi which are commented out. The configuration settings for using the sensehat are contained in the sensehat_config folder. In particular the overrides.cfg file in that folder is worth looking at. As supplied the columns in the sensehat are triggered by different frequency ranges starting from low at one side of the sensehat up to high at the other. In the last line of the overrides.cfg file there is a commented out line which allows a different channel mapping which gives a symmetrical output which you may find preferable. To try it out uncomment the line and restart the synchronized_lights program. Notice also the details of the audio card which has the internal name ‘Device’ which you can see if you type aplay -l in a terminal.
The only update I had to do to my hacked files to work with the latest lightshowpi was to replace a reference to import wiringpi2 as wiringpi with import wiringpi as wiringpi as this module appears to have changed its names between versions, and is installed by the latest lightshowpi.
If I had more time, further work on integrating the sensehat to lightshowpi could be done, so that it would fit into the latest and any subsequent version, but I leave that to any other interested party to take on.

Finally, if you like this project you may also be interested in a project to flash the lights on the PiHat Christmas Tree which I have recently described here

A visualiser for Sonic Pi 3

Every since Sonic PI had a transparency mode added (not available on the Raspberry Pi versions) I have been interested in adding a Visualiser graphics display as a backdrop. The built in Scope can give attractive displays, but I wanted something with a bit more colour, and which covered the whole screen. I did some experiments with the iTunes visualiser which added quite a nice backdrop, but only with a significant delay between the audio and the fluctuations of the display. The recent arrival of Sonic Pi 3 allowed for further possibilities, because it enabled the use of OSC messaging. I did a trawl of the internet and came across a promising looking processing sketch which produced a pattern which reacted to incoming audio. It was written several years ago and was only monochrome based. I played around with this, upgrading it to work on the latest version of Processing, and added some colour. I experimented with adding further  basic shapes to the display (it originally used an ellipse primitive, set up to give concentric circles, which could also be driven to produce a star burst effect). I added rectangles and star shapes and experimented with off-setting these as the program ran, and also with using more than one basic shape at the same time. I then added some code so that the sketch could receive incoming OSC messages sent from Sonic Pi 3, which could be used to control various parameters for the shapes, such as stroke width, colour, and offsets on the screen. I added further flexibility such as the ability to rotate the shapes, and to shift the whole display vertically and horizontally across the screen. The final setup works well with Sonic Pi 3, which controls the patterns both with the Audio signal it produces, and also with OSC messages which can be sent to the sketch display code. These can be timed appropriately with the musical content.

The code for the sketch is shown below

//Visualiser for use with Sonic Pi 3 written by Robin Newman, September 2017
// based on an original sketch
//Changes: changed to full screen, updated for Processing 3, added colour, added rectangle and star shapes
//added OSC input (from Sonic Pi) to alter parameters as it runs, removed slider inputs.
//input OSC:   /viz/float       updates STROKE_MAX, STROKE_MIN and audioThresh
//             /viz/pos         updates XY random offset values (can be zero)
//             /viz/col         updates RGB values
//             /viz/shapes      sets shapes to be used from S, E and R (or combinations thereof)
//             /viz/stardata    sets data for star shapes
//             /viz/rotval      turns rotation of shapes on/off
//             /viz/shift       turns XY shift across screen on/off
//             /viz/stop        initiates sending stop all signal back to Sonic Pi port 4557

import ddf.minim.analysis.FFT;
import ddf.minim.*;
import oscP5.*; //to support OSC server
import netP5.*;

Minim minim;
AudioInput input;
FFT fftLog;

int recvPort = 5000; //can change to whatever is convenient. Match with use_osc comand in Sonic Pi
OscP5 oscP5;
NetAddress myRemoteLocation; //used to send stop command b ack to Sonic PI

// Setup params
color bgColor = color(0, 0, 0);

// Modifiable parameters
float STROKE_MAX = 10;
float STROKE_MIN = 2;
float audioThresh = .9;
float[] circles = new float[29];
float DECAY_RATE = 2;
//variables for OSC input
float [] fvalues = new float[5]; //STROKE_MAX, STROKE_MIN,audioThresh values
int [] cols = new int[3]; //r,g,b colours
int [] positions = new int[2];// random offset scales for X,Y
int [] stardata = new int[4];// data for star shape, number of points, random variation
int shiftflag = 0; //flag to control xy drift across the screen set by OSC message
int two = 0; //variable to force concentric shapes when more than one is displayed
String shapes = "E"; //shapes to be displayed, including multiples from S,E,R
int rotval =0;
int xoffset = 0,yoffset = 0;
int xdirflag = 1,ydirflag = 1;

void settings() {

void setup() {  
   myRemoteLocation = new NetAddress("",4557); //address to send commands to Sonic Pi
  minim = new Minim(this);
  input = minim.getLineIn(Minim.MONO, 2048); //nb static field MONO referenced from class not instance hence Minim not minim

  fftLog = new FFT( input.bufferSize(), input.sampleRate()); //setup logarithmic fast fourier transform
  fftLog.logAverages( 22, 3); // see

  ellipseMode(RADIUS); //first two coords centre,3&4 width/2 and height/2
  cols[0] = 255;
  positions[0] = 50;
  /* start oscP5, listening for incoming messages at recvPort */
  oscP5 = new OscP5(this, recvPort);

void draw() {
  //calculate changing xy offsets: shiftflag set to 0 to siwtch this off
  xoffset += 10*xdirflag*shiftflag;
  yoffset += 10*ydirflag*shiftflag;
  if(shiftflag==0){xoffset=0;yoffset=0;} //reset offset values to zero if shifting is off
  //reverse directions of shifting when limits reached
  if (xoffset >displayWidth/3){xdirflag=-1;}
  if (xoffset < -displayWidth/3){xdirflag=1;} if (yoffset > displayHeight/3){ydirflag=-1;}
  if (yoffset < -displayHeight/3){ydirflag=1;}
  //transform to new shift settings
  translate(displayWidth/2+xoffset, displayHeight/2+yoffset); //half of screen width and height (ie centre) plus shift values

  //optional rotate set by OSC call
  //get limits for stroke values and audiThreshold from OSC data received
  //println("fvalues: ",STROKE_MIN,STROKE_MAX,audioThresh); //for debugging

  // Push new audio samples to the FFT

  // Loop through frequencies and compute width for current shape stroke widths, and amplitude for size
  for (int i = 0; i < 29; i++) {

    // What is the average height in relation to the screen height?
    float amplitude = fftLog.getAvg(i);

    // If we hit a threshold, then set the "circle" radius to new value (originally circles, but applies to other shapes used)
    if (amplitude < audioThresh) { circles[i] = amplitude*(displayHeight/2); } else { // Otherwise, decay slowly circles[i] = max(0, min(displayHeight, circles[i]-DECAY_RATE)); } pushStyle(); // Set colour and opacity for this shape circle. (opacity depneds on amplitude) if (1>random(2)) {
      stroke(cols[0], cols[1], cols[2], amplitude*255);
    } else {
      stroke(cols[1], cols[2], cols[0], amplitude*255);
    strokeWeight(map(amplitude, 0, 1, STROKE_MIN, STROKE_MAX)); //weight stroke according to amplitude value

    if (shapes.length()>1) { //if more than one shape being drawn, set two to 0 to draw them concentrically
      two = 0;
    } else {
      two = 1;
    // draw current shapes
    if (shapes.contains("e")) {
      // Draw an ellipse for this frequency
      ellipse(random(-1, 1)*amplitude*positions[0]*two, random(-1, 1)*amplitude*positions[1]*two, 1.4*circles[i], circles[i]);
    if (shapes.contains("r")) {
      rect( random(-1, 1)*amplitude*positions[0]*two, random(-1, 1)*amplitude*positions[1]*two, 1.4*circles[i], circles[i]);
    if (shapes.contains("s")) {
      strokeWeight(3); //use fixed stroke weight when drawing stars
      //star data Xcentre,Ycentre,radius1,radius2,number of points
      star(random(-1, 1)*amplitude*positions[0]*two, random(-1, 1)*amplitude*positions[1]*two, circles[i]*stardata[0], circles[i]/stardata[1], int(stardata[2]+random(stardata[3])));

    //System.out.println( i+" "+circles[i]); //for debugging
  } //end of for loop

void oscEvent(OscMessage msg) { //function to receive and parse OSC messages
  System.out.println("### got a message " + msg);
  System.out.println( msg);
  System.out.println( msg.typetag().length());

  if (msg.checkAddrPattern("/viz/float")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      fvalues[i] = msg.get(i).floatValue();
      System.out.print("float number " + i + ": " + msg.get(i).floatValue() + "\n");

  if (msg.checkAddrPattern("/viz/pos")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      positions[i] = msg.get(i).intValue();
      System.out.print("pos number " + i + ": " + msg.get(i).intValue() + "\n");

  if (msg.checkAddrPattern("/viz/col")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      cols[i] = msg.get(i).intValue();
      System.out.print("col number " + i + ": " + msg.get(i).intValue() + "\n");
  if (msg.checkAddrPattern("/viz/shapes")==true) {
    //for(int i =0; i<msg.typetag().length(); i++) {
    // shapes += msg.get(i).stringValue().toLowercase();      
    System.out.print("shapes code "+ shapes + "\n");
  if (msg.checkAddrPattern("/viz/stardata")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      stardata[i] = msg.get(i).intValue();
      System.out.print("stardata number " + i + ": " + msg.get(i).intValue() + "\n");
  if (msg.checkAddrPattern("/viz/rotval")==true) {
    rotval =msg.get(0).intValue();
    System.out.print("rotval code "+ rotval + "\n");
  if (msg.checkAddrPattern("/viz/shift")==true) {
    shiftflag =msg.get(0).intValue();
    System.out.print("shiftflag code "+ shiftflag + "\n");
  if (msg.checkAddrPattern("/viz/stop")==true) {
    kill(); //stop Sonic Pi from running

//function to draw a star (and polygons)
void star(float x, float y, float radius1, float radius2, int npoints) {
  float angle = TWO_PI / npoints;
  float halfAngle = angle/2.0;
  for (float a = 0; a < TWO_PI; a += angle) {
    float sx = x + cos(a) * radius2;
    float sy = y + sin(a) * radius2;
    vertex(sx, sy);
    sx = x + cos(a+halfAngle) * radius1;
    sy = y + sin(a+halfAngle) * radius1;
    vertex(sx, sy);

void kill(){ //function to send stop message to Sonic Pi on local machine
  OscMessage myMessage = new OscMessage("/stop-all-jobs");
   myMessage.add("RBN_GUID"); //any value here. Need guid to make Sonic PI accept command
  oscP5.send(myMessage, myRemoteLocation); 

The basis of a visualiser depends on doing a fast fourier transform analysis of the incoming audio, and calculating amplitudes related to the different frequency components of the audio, which is continuously monitored input buffer by input buffer. I don’t intend togo anywhere near the complex mathematics involved, but there are a lot of useful articles at different levels which you can read on the subject. I quite liked this one on the Fourier Transform. Also it is useful to look at the documentation of the minim library analysis section if you want more detailed information on the calls employed.
You may find it easier to look at the original sketch from which I started before taking on board the additions I have added to make the sketch more flexible and wide ranging.
I have added various transformations. Starting at the beginning of the main draw() function there are x and y offsets which increase each time the loop iterates, until a maximum offset is reached, when they reverse in direction. This causes the shapes to move smoothly left and right and up and down the screen. a shiftflag eanbles this to be siwtched on and off by one of the control OSC messages.
There follows an optional rotate command which can rotate the axis of the shapes being drawn, again controlled by an incoming OSC message.
Next values for setting the limits on the stroke size being used to render the shapes are read from data received by an OSC message, together with an audioThreshold setting.
A buffer from the input audio is now processed, and amplitude values for different frequency ranges are stored in an array of “circle” settings. NB the name circles is used for the variable as this was the only shape used in the original.Perhaps it might be better names shapes() now as there are three different classes of shapes used. A new value for the “radius” is stored if it is less than the audioThreshold setting, otherwise, a “decayed” value of the currently stored value from the previous iteration is stored. (suitable minimum values are set).
rgb colour values are set using values received from an OSC message, and these are then swapped at random, before setting the stroke colour attributes  to be used.
Next a flag two is set according to whether  one or more than one shapes have been selected. In the latter case the shapes are forced to be drawn concentrically, by nullifying the offset values by setting two = 0. The selected shapes are then drawn, before the loop starts a further iteration.

The oscEvent(OscMessage msg) function is triggered when an OSC message is received. It contains sections to parse the various OSC messages which can be sent from Sonic PI to the processing sketch. The parameters for each command are used to update various lists containing information used by the draw cols[ ] holds rgb values, startdata[ ] holds the parameters for the star shapes, fvalues[ ] holds the floating point values for the STROKE_MAX, STROKE_MIN  and audioThresh settings. These and other similar settings are updated when the relevant OSC messages are received, so Sonic PI can control the operation of the sketch as it runs.
The star functions draws the star shape. It is lifted straight from the star example here
The final function kill( ) is used to send a /stop-all-jobs OSC message back to Sonic PI to stop all programs running on that machine. It can be triggered by a /viz/stop OSC message being sent from Sonic PI to the Sketch.

As far as Sonic Pi is concerned, it produces two sorts of input. First the audio that it produces is fed back to the sketch which looks at the default audio input. On my Mac I used the program Loopback ( ) to perform this. This is a paid for program, but you can use it for free for 10 minutes or so at a time.It is based on the previous free SoundFlower utility, but this has not been fully updated for recent MacOS and you may find it difficult to get it to work instead. The setup I used is shown below:Note that Sonic Pi is added as a Source and that its output is monitored through the speakers, so that the audio is fed both there and to the processing sketch. This loopbackdevice will appear in the list of devices in the MIDI audio setup program, and should be selected as the default input device,

Secondly, Sonic PI is used to send OSC messages to the processing sketch to control its various parameters. this can be done by sending “one off” messages or by putting the message sender into a live loop, sending messages at regular intervals. An example is shown below, where the OSC messages are combined with the program producing the music, but they can  be run as a separate program in a different buffer, which is an advantage if you are visualising a linear piece and do not want to restart it every time you press run to update the OSC messages sent.

#Program to drive Sonic Pi 3 visualiser written in "processing"
#by Robin Newman, September 2017
#see article at
#set up OSC address of processing sketch
use_osc '',5000
#select shapes to show
osc "/viz/shapes","e"  #"s" "e" "r" Star,Ellipse, Rectangle or combination
sleep 0.1

live_loop :c do
  #choose starting colour for shapes
  osc "/viz/col",rrand_i(0,64),rrand_i(128,255),rrand_i(0,255)
  sleep 0.1

live_loop :f do
  #set Stroke max min widths and audioThreshold
  osc "/viz/float",([8.0,5.0,3.0].choose),[1.0,2.0].choose,(0.4+rand(0.3))
  sleep 2

#set range of random positional offset (can be 0,0)
#automatically disabled when showng more than one shape
osc "/viz/pos",20,0

#control "bouncing" shapes around the screen 1 for on 0 for off
osc "/viz/shift",0

live_loop :s do
  #setup star data inner/outer circle radius, number of points
  #and random variation of number of points
  osc "/viz/stardata",[1,2].choose,[1,2,3].choose,5,2
  sleep 4

rv=0 #variable for current rotation
live_loop :r do
  rv+=5*[-8,1].choose # choose rotation increment
  osc "/viz/rotval",rv #change rv to 0 to disable rotation
  sleep 0.1

#Now setup the sounds to play which will trigger the visualiser
use_bpm 60
set_volume! 5
use_random_seed 999

with_fx :level do |v|
  control v,amp: 0 #control the volume using fx :level
  sleep 0.1
  in_thread do #this loop does the volume control
    control v,amp: 1,amp_slide: 10 #fade in
    sleep 140
    control v,amp: 0,amp_slide: 10 #fade out
    sleep 10
    osc "/viz/stop" #send /viz/stop OSC message to sketch
    #sketch sends back a /stop_all_jobs command to port 4557
  #This drum loop is written by Eli see!topic/sonic-pi/u71MnHnmkVY
  #used with his permission. I liked it, and it has good percussive output
  #to drive a visualiser
  live_loop :drums do
    this_sample = [:loop_compus, :loop_tabla, :loop_safari].ring
    start = [ 0.0 , 0.125 , 0.25 , 0.375 , 0.5 , 0.625 , 0.75 , 0.875 ].ring
    sample this_sample.look , beat_stretch: 4, start: start.look, rate: 0.5
    sleep 1

As this program runs, you can alter the parameters eg shape(s) chosen, shift parameter etc. and rerun. Effectively live coding the visualiser. The program uses a great percussion loop written by Eli, which he said I might use.!topic/sonic-pi/u71MnHnmkVY

There is a video of the program in operation on youtube here

and you can download the code for the sketch and Sonic Pi programs here

You can download and install Processing from

You will also have to install the libraries Minim and oscP5 from the Sketch=>Import Library… menu.
To use, set up the loopback audio and select it as the default input device. Load and play the sketch in processing, then run the Sonic Pi program on the same computer. You can adjust the transparency of the Sonic Pi screen on the Preferences Visuals tab to make it semi transparent, or minimise Sonic Pi once it is running, if you are not going to do live coding of the control OSC messages.

Sonic Pi 3 drives the LEDs on pi-topPULSE module

The new pi-topPULSE module contains a 7×7 LED array, a microphone and an audio amplifier. The latter can be used by Sonic Pi as its output audio path, and Sonic PI version 3 can also be used to control the LEDs on the PULSE module using OSC messages, which can be received by a python program which decodes them, and uses the commands to control the LEDs.

I have written a full article giving a detailed explanation of how this is done, which you can read here.

There is also a link in the article to the code which is used, and to a video of the program in action on youtube.